Adding port, port number, port description implementations and related tests.
diff --git a/net/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java b/net/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java
index c171098..c434ff5 100644
--- a/net/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java
+++ b/net/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java
@@ -1,7 +1,32 @@
 package org.onlab.onos.net.device;
 
+import com.google.common.collect.ImmutableSet;
+import org.onlab.onos.net.Port;
+import org.onlab.onos.net.PortNumber;
+
+import java.util.Set;
+
 /**
  * Default implementation of immutable port description.
  */
 public class DefaultPortDescription implements PortDescription {
+
+    private final PortNumber number;
+    private final Set<Port.State> state;
+
+    public DefaultPortDescription(PortNumber number, Set<Port.State> state) {
+        this.number = number;
+        this.state = ImmutableSet.copyOf(state);
+    }
+
+    @Override
+    public PortNumber portNumber() {
+        return number;
+    }
+
+    @Override
+    public Set<Port.State> portState() {
+        return state;
+    }
+
 }